The present invention relates to a rhodium colloid which is useful as a hydrosilylation catalyst for silicon hydride having two or three hydrogen atoms attached to silicon. More particularly, the present invention relates to the reaction of rhodium trichloride with certain silicon hydride to produce a rhodium colloid.
Prior to the present invention as shown by Lewis, U.S. Pat. No. 4,681,963, platinum colloids were found to be superior hydrosilylation catalysts for effecting the addition of silicon hydride to an olefin including vinyl silicon materials. In certain situations however, particularly where a poly-addition reaction was necessary such as when using a silicon hydride having more than one hydrogen atom attached to silicon such as two or three hydrogen atoms, the employment of the platinum colloids was less effective. As a result, it was difficult to effect addition between silicon polyhydrides such as C.sub.6 H.sub.13 SiH.sub.3 to olefins such as 1-octene to make tetraalkyl-substituted silanes useful as hydraulic fluids and lubricants.
Silahydrocarbons have been made by the use of a rhodium-containing catalyst having a triphenylphosphine ligand as shown by Onepchenko et al., U.S. Pat. No. 4,572,791. Although the silahydrocarbons can be made by the Onepchenko et al. method, it requires an expensive catalyst, such as chloro(tristriphenylphosphine)rhodium(I) and the hydrosilylation reaction must be performed under a nitrogen atmosphere. Another hydrosilylation procedure utilizing a rhodium catalyst is shown by Chalk et al., U.S. Pat. No. 3,296,291. Chalk et al. utilizes an aliphatic alcohol to solubilize the rhodium chloride prior to contacting it with the silicon hydride reactant or the olefin reactant during the hydrosilylation procedure. Althou-gh effective results are achieved by the Chalk et al. method, reduced silahydrocarbon yields can result because the aliphatic alcohol can react directly with the silicon hydride before it has a chance to react with the olefin. It would be desirable, therefore, to provide a method for making silahydrocarbon based on the use of polyhydric silicon materials in combination with olefins without the use of expensive catalyst or reactants or conditions which render the procedure economically unattractive.
The present invention is based on my discovery that rhodium trichloride can be reacted under ambient conditions directly with silicon hydride having no more than two monovalent hydrocarbon radicals attached to silicon to produce a rhodium colloid which exhibits superior effectiveness as a hydrosilylation catalyst under ambient conditions with silicon hydride having two or three hydrogen atoms attached to silicon.